1. Field of the Invention
The present invention relates to an acquisition method of a charged particle beam deflection shape error, and a charged particle beam writing method.
2. Description of Related Art
The lithography technique that advances microminiaturization of semiconductor devices is extremely important as being a unique process whereby patterns are formed in the semiconductor manufacturing. In recent years, with high integration of LSI, the line width (critical dimension) required for semiconductor device circuits is decreasing year by year. For forming a desired circuit pattern on such semiconductor devices, a master or “original” pattern (also called a mask or a reticle) of high accuracy is needed. Thus, the electron beam (EB) writing technique, which intrinsically has excellent resolution, is used for producing such a highly precise master pattern.
FIG. 8 is a schematic diagram explaining operations of a variable shaped electron beam (EB) writing or “drawing” apparatus. As shown in the figure, the variable shaped electron beam writing apparatus operates as described below. A first aperture plate 410 has a quadrangular opening 411 for shaping an electron beam 330. A second aperture plate 420 has a variable-shape opening 421 for shaping the electron beam 330 having passed through the opening 411 of the first aperture plate 410 into a desired quadrangular shape. The electron beam 330 emitted from a charged particle source 430 and having passed through the opening 411 is deflected by a deflector to pass through a part of the variable-shape opening 421 of the second aperture plate 420, and thereby to irradiate a target object or “sample” 340 placed on a stage which continuously moves in one predetermined direction (e.g. the x direction) during the writing. In other words, a quadrangular shape that can pass through both the opening 411 and the variable-shape opening 421 is used for pattern writing in a writing region of the target object 340 on the stage continuously moving in the x direction. This method of forming a given shape by letting beams pass through both the opening 411 of the first aperture plate 410 and the variable-shape opening 421 of the second aperture plate 420 is referred to as a variable shaped beam (VSB) method.
FIG. 9 shows an example of an evaluation pattern for evaluating a deflection shape of a beam shot written on a target object. In a writing apparatus, a plurality of evaluation patterns are respectively written at a plurality of positions arranged regularly in a deflection region deflected by a deflector in order to secure a writing position accuracy. FIG. 9 show the case where five by five (5×5) evaluation patterns are written in a subfield in two stage deflection, in such a way as to be arranged regularly, each evaluation pattern being composed of four quadrangular shot figures. The reason for a plurality of evaluation patterns being written is to evaluate change of the dimension and shape depending upon deflection positions. A shift amount of a deflection position in the deflection region is checked by measuring the position of each evaluation pattern, and a deflection region shape is also checked based on the shape of the figure which is formed by considering all the evaluation patterns as one figure.
However, with the miniaturization of patterns in recent years, reducing the deflection region is on the increase in order to perform writing at a more highly accurate writing position (refer to, e.g., Japanese Patent Application Laid-open (JP-A) No. 2011-228498). Therefore, it is becoming difficult to arrange many evaluation patterns in one deflection region such as shown in FIG. 9. For example, the deflection region has been reduced even to the size in which only about one-by-one (1×1) or two-by-two (2×2) evaluation patterns can be arranged in one deflection region. With such a number of evaluation patterns, it is difficult to specify a deflection shape of high precision.